Role of Particles in Flame Inhibition by Iron Pentacarbonyl.
Role of Particles in Flame Inhibition by Iron
Rumminger, M. D.; Linteris, G. T.
Halon Options Technical Working Conference.
Proceedings. HOTWC 1999. April 27-29, 1999, Albuquerque,
NM, 511-521 pp, 1999.
flame extinguishment; chemical inhibition; flame
chemistry; halon alternatives
Certain metallic compounds have been found to be
substantially more effective flame inhibitors than
halogen-containing compounds. In particular, iron
pentacarbonyl (Fe(CO)5) was found to be one of the
strongest inhibitors--up to two orders of magnitude more
effective than CF3Br at reducing the burning velocity of
premixed hydrocarbon-air flames. Although Fe(C0)5 is
highly toxic, understanding its inhibitory effect could
lead to development of effective non-toxic agents.
Measurements of Fe(CO)5-inhibited premixed flames have
shown that the inhibition varies with the Fe(CO)5
concentration: at low mole fraction the burning velocity
is strongly dependent on inhibitor mole fraction, while
at high Fe(CO)5 mole fraction the burning velocity is
nearly independent of inhibitor mole fraction. A
critical part of the research on Fe(CO)5 is to
understand iron pentacarbonyl's diminishing
effectiveness at high mole fraction in order to avoid
similar behavior in future fire suppressants. A
plausible but unconfirmed explanation for iron
pentacarbonyl's reduced effectiveness under certain
conditions is that particles form, thus reducing the
gas-phase mole fraction of active inhibiting species.
To investigate this possibility, we use laser-light
scattering to measure particles in premixed flames with
added Fe(CO)5 and determine if the conditions of high
particle concentration correspond to the regions of
reduced inhibition effect. Alternatively, if there is
high particle density for conditions at which Fe(CO)5
has a strong inhibition effect, then the search for
halon alternatives could be directed toward chemicals
that produce similar condensed-phase compounds.